GAZETTE: One group highlighted in COSMOS-Web was made up of people with cardiovascular disease, among whom the multivitamin seemed to produce a particularly strong effect. You were able to rescue cognitive function in that group, which began lower than the larger sample’s baseline, and bring them back to baseline within a year. What does this say about nutrition and cardiovascular disease?

MANSON: There are many nutritional factors that are important in reducing risk of cardiovascular disease. And it is likely that people with a history of cardiovascular disease have lower nutrient status, at least for certain selected nutrients. That may be why they’re benefiting more. It’s also possible that, because of medications they’re taking or other needs that they have, they benefit more from the multivitamins. We want to drill down more deeply on those findings, because they were very consistent between COSMOS-Mind and COSMOS-Web.

GAZETTE: I remember talking to you previously about how the landscape of supplements is something like the Wild West, with lots of claims and little science.

MANSON: It still is.

GAZETTE: You’ve taken a hard look at several supplements over the years. Have any general guidelines emerged from your studies?

MANSON: There’s a dizzying array of products and most are not tested for safety or efficacy before they get on the shelf. We test dietary supplements that look promising according to several lines of evidence — biological mechanisms, observational studies — and then we do rigorous, randomized clinical trials, which are the gold standard for testing cause and effect.

I think there are several overriding themes. When it comes to dietary supplements, more is not necessarily better and can be worse. One reason multivitamins are surfacing as providing benefits for cognition may be that they’re a comprehensive supplement of daily intake values, not megadoses, of these micronutrients. Once you get into megadoses — and many dietary supplements on the market are very high doses of isolated micronutrients — then it’s more likely that you’ll see risks and toxicities occurring. So, unless there’s a clear indication to take more than the recommended dietary allowance or moderate doses of nutrients, it’s best to avoid megadosing.

Another point is that multivitamins and other dietary supplements should not be perceived as a substitute for a healthy diet or a healthy lifestyle, but as a complementary strategy. Clinicians are sometimes concerned that recommending dietary supplements will lead to complacency about healthy diets and regular physical activity. Nothing is going to replace a healthy lifestyle in terms of fending off chronic diseases and achieving a longer health-span. It is really important that people understand that.

These two cognition trials in COSMOS suggest that multivitamins can be a safe, affordable, and accessible strategy for protecting cognitive health in older adults. Based on the consistency of the findings, I think we can now say, “A multivitamin a day helps keep memory loss at bay.” I do think the evidence for that is exciting, compelling, and warrants further study to identify those most likely to benefit.